Since organic electroluminescence devices (hereinafter also referred to as “devices” or “organic EL devices”) are capable of obtaining high luminance light emission by low voltage driving, they are actively researched and developed in recent years. An organic electroluminescence device generally includes a pair of electrodes and at least one organic layer including a light-emitting layer between the pair of electrodes, and electrons injected from the cathode and holes injected from the anode are recombined in the organic layer including a light-emitting layer, and generated energy of exciton is used for emission of light.
In recent years, efficiency of devices has been advanced by the use of phosphorescent materials. For example, an organic electroluminescence device excellent in light emission efficiency and durability of device by using iridium complex or platinum complex as the phosphorescent materials is proposed.
Further, doping type devices using a light-emitting layer obtained by doping a light-emitting material in a host material are widely adopted.
For example, iridium complexes containing a condensed azole ligand which are highly durable and capable of blue light emission are disclosed in Patent Document 1.
It has been conventionally considered that when materials for use in organic EL devices such as light-emitting materials contain impurities, durability of devices is banefully influenced. Accordingly, techniques capable of reducing impurities in the materials and increasing the purity of the materials are proposed.
For example, for the purpose of the improvement of durability of a device, a luminescence device is disclosed in Patent Document 2, in which at least one organic compound layer contains a metal-coordinated compound and the content of the decomposed product or the raw material of the metal-coordinated compound in the organic compound layer is 0.5% by mass or less.